1. Field of the Invention
This invention is related to an apparatus or system for wet processing, especially for use in a washing or etching process of substrates in semiconductor device fabrication. The present invention provides an apparatus and system which continuously processes the substrates one by one.
2. Description of the Prior Art
In semiconductor manufacturing there are many wet processes, such as washing and etching of the substrates. For such processes, a batch process has been used, in which a number of substrates are placed in a bucket and etched in the basket, or the substrates are placed on a rack and immersed in the etchant. In such batch processes, it is difficult to precisely control the etching because during the time the etchant in the bucket is replaced by water or the rack is taken out from the etchant and immersed in water, the etching of the substrates proceeds. Moreover, it is difficult to process the surface uniformly, since the etchant trickles from one side of the substrate when the substrate is lifted from the etchant.
In some cases, the surfaces of the substrates are polluted or oxidized by air during the time they are moved from one process to the next process. Therefore, if the progress of a process is delayed for some reason, the preprocessing is again required. The above problems have an undesirable influence on the yield and dispersion of the characteristics of products.
In order to overcome the above problems, recently the process for fabricating semiconductor devices has shifted from batch processing to one by one processing.
Fundamental in the one by one chemical processing is to hold the substrate with a chuck and treat the substrate in a cup containing the chemicals (cup treatment), or spray the chemicals on the surface of the substrate (spray treatment).
One example of cup treatment is shown schematically in FIG. 1. The cup 1 is filled with the chemicals of etchant or water 2 which is added from the bottom of the cup 1 and overflows from the edge of the cup 1. The arrow lines 5 indicate the direction of flow of the etchant or water. The substrate 4 is fixed to the chuck 3 by a vacuum, for example, and is immersed into the etchant 2. The chuck 3 is rotated about its axis as shown by the arrow 6, in order to treat the surface of the substrate uniformly.
A typical example of spray treatment is shown schematicaly in FIG. 2. The substrate 4 is fixed on the chuck 3 and rotated about the axis as indicated by the arrow 6. The chemicals or water 2 is sprayed on the surface of the substrate 4 from a nozzle 7. A cover 8 prevents the splash of chemicals.
In such prior art systems, the substrates or slices to be processed are held by vacuum chucks, for example, and it is, therefore, impossible to treat both sides of the slice at the same time. Thus, this process can not be applied to specific treatments which require treatment of both sides of the slices at the same time.